Highly Efficient Deep-Blue OLEDs using a TADF Emitter with a Narrow Emission Spectrum and High Horizontal Emitting Dipole Ratio

Hyoungcheol Lim; Hyung Jin Cheon; Seung-Je Woo; Soon-Ki Kwon; Yun-Hi Kim; Jang-Joo Kim

doi:10.1002/adma.202004083

Highly Efficient Deep-Blue OLEDs using a TADF Emitter with a Narrow Emission Spectrum and High Horizontal Emitting Dipole Ratio

Adv Mater. 2020 Nov;32(47):e2004083. doi: 10.1002/adma.202004083. Epub 2020 Oct 20.

Authors

Hyoungcheol Lim¹, Hyung Jin Cheon², Seung-Je Woo¹, Soon-Ki Kwon³, Yun-Hi Kim², Jang-Joo Kim^{1

4}

Affiliations

¹ Department of Materials Science and Engineering, Seoul National University, Seoul, 08826, South Korea.
² Department of Chemistry and RIGET, Gyeongsang National University, Jinju, 52828, South Korea.
³ Department of Materials Engineering and Convergence Technology and ERI, Gyeongsang National University, Jinju, 52828, South Korea.
⁴ Research Institute of Advanced Materials (RIAM), Seoul National University, Seoul, 08826, South Korea.

PMID: 33079442
DOI: 10.1002/adma.202004083

Abstract

New blue (DBA-SAB) and deep-blue (TDBA-SAF) thermally activated delayed fluorescence (TADF) emitters are synthesized for blue-emitting organic-light emitting diodes (OLEDs) by incorporating spiro-biacridine and spiro-acridine fluorene donor units with an oxygen-bridged boron acceptor unit, respectively. The molecules show blue and deep-blue emission because of the deep highest occupied molecular energy levels of the donor units. Besides, both emitters exhibit narrow emission spectra with the full-width at half maximum (FWHM) of less than 65 nm due to the rigid donor and acceptor units. In addition, the long molecular structure along the transition dipole moment direction results in a high horizontal emitting dipole ratio over 80%. By combining the effects, the OLED utilizing DBA-SAB as the emitter exhibits a maximum external quantum efficiency (EQE) of 25.7% and 1931 Commission Internationale de l'éclairage (CIE) coordinates of (0.144, 0.212). Even a higher efficiency deep blue TADF OLED with a maximum EQE of 28.2% and CIE coordinates of (0.142, 0.090) is realized using TDBA-SAF as the emitter.

Keywords: deep-blue emitters; horizontally oriented emitting dipole moments; organic light-emitting diodes; rigid structures; thermally activated delayed fluorescence.

Abstract

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